Mariska Hargitay's Health Mystery Revealed

Since January, when her rep announced Mariska Hargitay had suffered a partially collapsed lung, information about the nature of the Law & Order: SVU‘s star condition has been scant, until now.

During a dinner in Manhattan for the American Ballet Theater on Monday, Hargitay, 45, told PEOPLE: “I’ve been doing my own stunts on the show for 10 years. I fell wrong, basically. I collapsed my lung doing a stunt.”

Hargitay underwent surgery in January, then returned to work on her NBC series soon after – only to check back into the hospital on March 3, at which time her rep said: “She is undergoing routine tests and expects to be feeling better soon.”

A March 9 statement said, “Mariska is recovering well and is expected to return to SVU in the next couple of weeks.” On March 23, PEOPLE reported she was back on the set.

And now? “I’m 100 percent,” a spectacular-looking Hargitay, in a long gown by Caroline Herrera (who helped sponsor the event), told PEOPLE at the dinner, where Caroline Kennedy introduced Michelle Obama, who in turn introduced the young performers of the ABT’s Jacqueline Kennedy Onassis School.